The present invention relates generally to hydraulic pumps, and more particularly to a hydraulic pump assembly which has incorporated therein a splined insert component.
Conventional hydraulic pumps include an input or power shaft defining a splined connection with a cylinder block or barrel. Pumping pistons are reciprocatingly mounted within cylinder bores of the pump cylinder block or barrel, and the piston rods have spherical or ball-shaped end portions which are disposed within recessed portions of shoes mounted upon the pump swashplate. In accordance with a first technique conventionally employed for securing the shoes upon the pump swashplate, the flat or planar sides or surfaces of the shoes are mounted upon corresponding flat or planar surfaces of the swashplate and are retained thereon with a fixed clearance by suitable clamping mechanisms. While such hydraulic pump assemblies have, of course, exhibited satisfactory operational performance, it is sometimes difficult to attain the fixed clearance between the shoes and the swashplate in accordance with the desired or requisite manufacturing tolerances. In addition, the various components of the assemblies are also difficult or tedious to in fact assemble, and the assembly procedures are therefore costly in terms of man-hours required to be expended.
second system or technique conventionally employed for securing the shoes upon the pump swashplate is disclosed, for example, within U.S. Pat. No. 5,784,949 which issued to Ryken et al. on Jul. 28, 1998. In accordance with this system or technique, a plurality of axially extending pins are disposed within axially extending holes or bores as to in effect be interposed between the internal peripheral bore portion of a cylinder block and the external peripheral portion of a splined input shaft. Washers are forced into contact with first ends of pins by a coil spring, and the opposite ends of the pins engage a ball guide which, in turn, engages a guide member. The guide member effectively clamps or secures shoe plates or slipper retaining rings through slippers. Again, as was the case with the first conventional device or technique used for mounting and retaining the shoes upon the pump swashplate, while such hydraulic pump assemblies have of course exhibited satisfactory operational performance, the various components of the assemblies are also difficult or tedious to in fact assemble, and in addition, the pins exhibit excessive wear.
A need therefore exits in the art for a new and improved hydraulic pump assembly which effectively overcomes or eliminates the aforenoted problems or assembly disadvantages or drawbacks characteristic of the known or conventional prior art hydraulic pump swashplate and piston rod assemblies.
The present invention is directed to overcoming one or more of the problems as set forth above.
The foregoing need is achieved in accordance with the principles and teachings of the present invention through the provision of a new and improved hydraulic pump assembly which comprises a cylinder block defining an axis and having an inner peripheral splined portion; a plurality of piston cylinders defined within the cylinder block and arranged within a circumferential array about the axis of the cylinder block for respectively housing a plurality of pumping pistons; an input shaft having an axial extent and disposed substantially coaxially within the cylinder block, the input shaft having an outer peripheral splined portion; a coil spring disposed around the input shaft at a first axial position thereof; a washer disposed around the input shaft at a second axial position thereof for biasing shoe plates into engagement with swashplate shoes; and an annular sleeve member disposed around the input shaft and axially interposed between the coil spring and the washer such that the coil spring axially biases the annular sleeve member into engagement with the washer, the annular sleeve member having an inner peripheral splined portion for splined engagement with the outer peripheral splined portion of the input shaft, and an outer peripheral splined portion for splined engagement with the inner peripheral splined portion of the cylinder block.